Step 1: Preparations before starting the MRI receiving coil connection line
Before starting the equipment with the MRI receiving coil connection line, check whether the voltage and frequency of the power supply line are normal, check whether all emergency stop switches are normal, and check whether the water cooling system pipeline connection is normal. Then turn on the power control switches of each channel in turn, start the helium compressor, and check the pressure of the helium compressor. If the pressure of the helium compressor is lower than the normal range, it is necessary to replenish helium with a purity of 99.999%. Check the outlet and return pressure of the water cooling system, and check the water temperature. Check the liquid helium capacity.
Step 2: Infusion of liquid helium
When filling, the operating space should be spacious and ventilated, with appropriate temperature and humidity, and a safe exit.
Operating points of liquid helium filling: If the liquid helium capacity is low, for safety, you should first release the current of the magnetic resonance receiver coil connecting wire magnet coil and then replenish the liquid helium. The release method is to replace the electrode, and the insertion and replacement action should be rapid and stable. , In order to prevent air from entering the magnet causing icing and even quenching. Before releasing and restoring the current, the air outlet pipe on the electrode and the quench tube should be short-circuited to prevent the excessive pressure in the magnet from quenching when the current is released and restored. If the liquid helium capacity is high, the liquid helium can be directly replenished without releasing current. Before replenishing, short-circuit the one-way valve between the magnet liquid helium volatilization outlet and the helium passage (recovery passage or emptying passage), and then short-circuit the helium pipe and quench pipe to balance the pressure in the magnet with the atmospheric pressure. The short-circuit time of the MRI receiver coil connection line should not be too long, so as to avoid air entering the magnet and causing icing or quenching. When the pressure inside and outside the magnet tank is balanced, fully open the liquid regulating valve of the siphon tube, and slowly insert the liquid inlet end into the bottom of the Dewar tank where the liquid helium is calm. When the sprayed gas turns into a white mist, close the valve immediately. And quickly insert the liquid outlet into the inlet of the helium pipe, and screw the connection pipe tightly, and then adjust the size of the liquid inlet valve by observing the pressure of the magnet pressure gauge.
After the connecting wire of the MRI receiving coil is turned on, eliminate the abnormal display of the meter.